From: William Grosso <wgrosso@...>
Date: 2006-09-14T00:28:29+09:00
Subject: Re: What does it take to make an object hashable, no really...

Tim Pease wrote:
> On 9/13/06, Just Another Victim of the Ambient Morality
> <ihatespam@rogers.com> wrote:
>>     Suppose I want to define a class and be able to use this class as 
>> a key
>> to a hash.  How does one do this?  ...And please test your response 
>> before
>> posting it.
> 
> Chapter 22 of the Programming Ruby, The Pragmatic Programmer's Guide
> 
> A key must respond to "hash" and the value returned must not change.
> 
> What is not in the book is that you must also provide an eql? method
> that evaluates to true when two objects are equivalent.
> 

More precisely: if two objects are equivalent, they should have the same
hash value, and eql? should return true.


Bill